Removal of metal comprising contaminants from petroleum oils



States This invention relates broadly to the removal of metalcomprising contaminants from petroleum oils. More particularly the invention is concerned with a new and unobvious method of upgrading a petroleum oil containing metal-comprising contaminants, e.g., such contaminants comprising metalloporphyrins, which comprises contacting said oil with a treating agent comprising essentially condensed polynuclear aromatic compound having a (3/11 ratio between about 1/1 and about 2.5/1 and an average molecular weight within the range Of from about 200 to about 600. The aforesaid contacting, as by admixing, is effected while the said oil and the said treating agent are in hot liquid state, e.g., while an admixture thereof is at a temperature within the range of, for instance, from about 550 F. to about 900 F., more particularly from about 700 F. to about 850 F. The hot treatment of the oil to be upgraded may be effected at atmospheric, subatmospheric or superatmospheric pressure.

it was known prior to the present invention that various solvents and other means could be used for the removal of metal contaminants from petroleum oils. For example, Patent No. 2,472,723 discloses that the detrimental etiects of-metal, metal oxide and metal-salt contaminants in feed stocks to fluid-catalyst cracking processes are substantially eliminated by continuously contacting the feed stock with a small quantity of contact clay such as that used in lube-oil contacting operations but having a substantially smaller particle size. Patent No. 2,847,35 4 discloses a process of upgrading a petroleum oil boiling within the range of from about 450 F. to about 1300 F. and which contains metal-comprising contaminants, said method comprising contacting such an oil with about 50 to 400 volume percent to either hydantoin or an alkyl-substituted hydantoin at a temperature Within the range of from about 80 F. to about 500 F., and segregating a treated oil. Patent No. 2,870,081 discloses a process of removing metal-containing contaminants from an oil which comprises subjecting such an oil to a direct voltage electrical fieldof at least 15,000 volts per centimeter for a time suificient to remove such contaminants from the said oil. Patent No. 2,911,355 discloses an improved fractionation method for effectively separating metal contaminants from gas oils. Patent No. 2,913,394 discloses the use of butyrolactone in removing metal contaminants from a hydrocarbon oil boiling within the range of from about 450 F. to about 1300 F.

The present invention is based on my discovery that metal-comprising contaminants (that is, contaminants wherein the metal impurity is present either in a free or a combined state) can be removed from a petroleum oil, and the said oil upgraded, as briefly described in the first paragraph of this specification and more fully hereinafter. The oil containing metal-comprising contaminants that can be upgraded in accordance with the present invention is any petroleum oil containing metal-comprising contaminants including those described in the aforementioned prior-art patents. Such contaminants include metalloporphyrins which are compounds formed by the combination of a porphyrin with a metal such as iron, copper, cobalt, nickel, silver, tin, zinc, manganese, magnesium, vanadium, etc. [Blakistons New Gould Medical Dictionary Illustrated, p. 724 (1956)]. The porphyrins include protoporphyrin, mesoporphyrin, hemaporphyrin, deuteroporphyrin, etioporphyrin, coproporphyrin, uroatent ice porphyrin, rhodoporphyrin, pyrroporphyrin, pyrroetioporphyrin, chlorophyllin and chlorophyll [The American Illustrated Medical Dictionary, 21st Edition, p. 1160 (1947)].

The petroleum oil containing metal-comprising contaminants that can be upgraded in accordance with the instant invention also includes residual stocks and heavy gas oil stocks containing such contaminants, as well as catalytic feed stocks containing a vanadium-comprising (or other metal-comprising) contaminant. The oil Which is treated in accordance with the present invention also includes those boiling within the range from about 450 F. to about 1300 F. and which contains one or more metal-comprising contaminants.

The metal-comprising contaminant that is present in a petroleum oil may be present in the original topped or untopped crude petroleum oil. However, the metal-comprising contaminant may be the result of the operating procedures to which the oil has been subjected, such as, the metal or metals that are removed from the equipment by erosion or corrosion during catalytic cracking. Metals present may include, for example, iron, nickel, copper, chromium, manganese, molybdenum, vanadium, etc. It is well known in the art of catalytic cracking that the presence of such metals, especially nickel and/ or vanadium, in free, oxide or other state is extremely detrimental to the efiiciency of the catalysts. For example, deterioration of catalyst selectivity with time can be caused by the presence of such catalysts (even in relatively small quantities) in the feed. The presence of sulfur as well as metals of the kind aforementioned are known to poison natural and synthetic catalysts. Also, the metal contaminants present in coker charge stocks concentrated in the coke produced therefrom. By removing the contaminants from the charge stocks the resulting coke can be upgraded from fuel quality to metallurgical quality. Hence there has been need in the art for a long time for some economical and efiicient means for removing metalcomprising contaminants from a petroleum oil and particularly from fractions or residua from such oils that are to be subjected to catalytic-cracking or coking techniques.

As was mentioned in the first paragraph of this specification, the treating agent employed in practicing the present invention is one which comprises essentially condensed polynuclear aromatic compound or substance having an atomic carbon to hydrogen (C/H) ratio between about 1/1 and about 2.5/1 and an average molecular weight Within the range or" from about 200 to about 600. Such condensed polynuclear aromatic compounds are produced, for example, as described in an article by Martin et al., Pitch Binder Coke Yields, Ind. and Eng. Chem, 50, 1, 33-40 (January 1948). They include compounds of the molecular structure represented by the top line and the top molecular sketch of FIGURE 5 on page 40 of the aforementioned publication. The sketch of the structure there shown is as follows:

Pitch binders, more particularly electrode pitch binders, comprising essentially condensed polynuclear aromatics having the C/H ratio and the average molecular weight needed for use as a selective solvent for metal-comprising contaminants in practicing the present invention can be produced. for example, by thermal cracking of selected petroleum fractions followed by heat-soaking. They also may be prepared by heat-soaking alone, for instance by heat-soaking under conditions whereby all material is kept in the liquid phase except low-boiling degradation products that are released continuously. One Way of accomplishing this is to keep materials of the desired boiling range in the liquid phase at the soaking temperature. Another way is to heat-soak at atmospheric pressure while continuously condensing the material of higher boiling range and returning it to the soaking zone.

More specific examples of pitches that can be used in practicing the instant invention are those obtained (a) by thermally cracking bubble-tower bottoms followed by heat-soaking and (b) by heat-soaking the same bubbletower bottoms without cracking. Both pitches have substantially the same properties, e.g., each has, by weight, about 14.1% benzene insolubles and about 1.5% quinoline insolubles. Another specific example is a pitch produced by heat-soaking an uncracked furfural extract, and which contains, by weight, about 24.7% benzene insolubles and about 3.4% quinoline insolubles. All of the foregoing specific examples of pitches comprise or are composed essentially of condensed polynuclear aromatic compound(s) having a C/H ratio between about 1/1 and about 25/1 and an average molecular weight within the range of from about 200 to about 600.

Additional and more specific properties of illustrative examples of treating agents that can be used in practicing the present invention are shown in Table I.

TABLE I Kind of Treating Agent Electrode Thermal Heavy Heavy Pitch Asphalt Thermal Coke]: Binder Gas Oil Gas Oil 5 Vol. Percent 882 10 Vol. Percent. 748 925 30 Vol. Percent- 804 1,007 Vol. Percent- 846 1,053 V01. Percent 886 1, 096 50 Vol. Pereent 936 1 1,146 Vol. Percent 968 1 At 87 percent.

Treating agents of the kind illustrated in Table I, as well as others employed in carrying the present invention into effect, can be produced, for example, by severe degradation of either virgin or catalytic petroleum oil stocks by catalytic and/or thermal cracking of such stocks. 60

Any suitable means can be used for contacting a petroleum oil containing metal-comprising contaminants with the treating agent comprised of condensed polynuclear aromatic compound or material that is employed in practicing the present invention and whereby the treated oil is upgraded by separating therefrom a substantial amount of the aforesaid contaminants. At least in some cases the sulfur content of the oil also is reduced by the treatment. For example, the treating agent and metalcontaminated petroleum oil can be batch-mixed and the insoluble material containing the higher content of metal comprising bodies allowed to settle. Thereafter the supernatant oil with lower content of metal-comprising bodies is separated from the settled material, e.g., by decantation, or be extracting the soluble mala ial with a suitable 75 solvent such as benzine, naphtha, etc., leaving the metalcomprising bodies in the unextracted phase.

Another method involves first treating an inactive catalyst, e.g., spent TCC catalyst, at about 700900 F., e.g., about 800 F. with a treating agent of the kind used in practicing this invention. The treated catalyst may contain, for example, from about 20% to about 60% by weight of the treated catalyst, of the treating agent. The thusly treated catalyst, which has been inactivated by the treatment, is then used to treat a petroleum oil containing a metal-comprising contaminant. Any suitable amount of such treated catalyst can be used, e.g., 1 part by volume of said catalyst to from 2 to 2000 parts by volume of oil. A substantial amount of the metal-comprising bodies in the petroleum oil that is undergoing treatment are deposited on the catalyst, which later is then separated by gravity or otherwise from the treated oil. v

The amount of treating agent employed can be varied as desired or as conditions may require. The main solvating component of the treating agent, and which selectively acts upon the metal-comprising contaminants, is the above-described condensed polynuclear aromatic compound(s). This polynuclear aromatic material may constitute, for example, from as low as 1 or 2% to by weight of the treating agent. The amount of polynuclear aromatic material that is employed (as such, i.e., 100%, or in a diluent) in treating a petroleum oil con taining metal-comprising contaminants may vary, for example, from 1% to 100% by weight of the said petroleum oil, these percentages being based on 100% of the aforementioned polynuclear aromatic material.

The temperature of the treatment also may vary widely depending, for instance, upon the particular treating agent employed, the particular petroleum oil being treated, the particular method used, etc. For instance, it may range from about 400 F. to about 1100 F., more particularly within the range of from about 550 F. to about 900 F., although higher or lower temperatures than those just mentioned can be used as desired or as conditions may require. Good results have been obtained at temperatures ranging from about 700 F. to 850 F. in the treatment of catalytic feed stocks, e.g., a stock containing a vanadium-comprising contaminant.

In order that those skilled in the art may better understand how the present invention can be carried into effect, the following examples are given by way of illustration and not by way of limitation. All parts and percentages are by weight unless otherwise stated. In all of the examples the particular treating agent employed comprised essentially condensed polynuclear aromatic compound or substance having an atomic C/ H ratio between about 1/1 and about 2.5/1 and an average molecular weight within the range of from about 200 to about 600.

Example 1 In this example 240 g. of Tia Juana residuum having a vanadium content of 396 ppm. was contacted for 1 hour in a shaker bomb at 750 F. with 60 g. of a pitch of the kind used in practicing this invention and wherein the weight percent of benzene insolubles was 25, specifically so-called Allied pitch. The mixture was poured into a separating funnel and the insolubles were allowed to settle out. The decanted liquid contained p.p.m. of vanadium. The material that separated out in the separating funnel contained 265 ppm. of vanadium. The coke contained 1550 ppm. of vanadium. The material that adhered to the walls of the bomb contained about 350 ppm. vanadium.

Example 2 In this example 240 g. of Tia Juana residuum was contacted for 1 hour in a shaker bomb at 750 F. with 60 g. of petroleum pitch containing 12.8% of benzene insolubles by weight. The mixture was poured into a separating funnel and the insolubles were allowed to settle out. The decanted liquid contained 141 ppm. of vanadium, while the residuum in the funnel contained 278 p.p.m. of vanadium.

Example 3 A series of three runs was carried out in which, in each case, 180 g. of Tia Juana residuum was heated for l an average molecular weight within the range of from about 200 to 600.

Example 9 was a control run and contained no treating agent.

The time and the temperature of heat-soaking the charge stock with the treating agent were, in all cases, 1 hour and 750 B, respectively.

1 Gas oil from thermal asphalt production was treating agent (see col. 3 of Table I for properties).

2 Heavy coker gas oil was treating agent (see col. 4 of Table I for properties). 9 No treating agent was used.

Same as in Example 3 with the exception that there was used 180 g. of Tia Juana residuum and 20 g. of Augusta SOV gas oil as the solvent for the metals-comprising Tia Juana residuum. A summary of the results is given below:

TABLE III Percent Temp, Vanadium, Insol., Per- Vanadium F. p.p.m. in Insolubles cent Wt. of from Liquid Charge Charge in Insol.

As a check to be sure that the treating agent was primarily responsible for the reduction of the metal-comprising contaminant in the Tia Juana residuum, 200 g. of Tia Juana residuum was heated alone in the shaker bomb for 1 hour with the following results:

At 550 F., 385 p.p.m. vanadium in liquid; no insolubles.

At 750 F., 410 p.p.m. vanadium in liquid; no insolubles.

At 800 F., 164 p.p.m. vanadium in liquid; 8.9 wt. percent insolubles.

The results of the treatment of various coker charge stocks with different treating agents of the kind used in practicing the present invention are shown in Table IV. In Examples 5 through 9 the kind of charge stock that was treated was Tia Juana residuum; in Example 10 it was Mid-Continent residuum; and in Example 11 it was East Providence gas oil. These charge stocks contain metal-comprising contaminants including metalloporphyrins. The particular treating agent employed is described in the footnotes to the table, and each comprised essentially condensed polynuclear aromatic material having a C/H ratio between about 1/1 and about 2.5/1 and Similar results are obtained, using a treating agent of the kind employed in the foregoing examples, in the treatment of petroleum oils containing in lieu of, or in addition to, a relatively large amount of vanadium as a contaminant, other metal contaminants found in petroleum oils, especially nickel, copper, chromium, manganese and/ or molybdenum.

The process of this invention is particularly eflective for the treatment of charge stocks to coking, i.e., high temperature thermal cracking, to produce solid petroleum coke. When metals are removed from such charge stocks the coke resulting from the process will be of a grade suitable for the manufacture of electrodes for use in the metallurgical industries. Otherwise, the coke may be only useful for fuel.

I claim:

1. The method of upgrading an asphaltic residual oil containing metal contaminants, said method comprising contacting said asphaltic residual oil with a treating agent comprising essentially condensed polynuclear aromatic compound having an atomic C/ H ratio between about 1/ 1 and about 25/1 and an average molecular weight within the range of from about 200 to about 600, said contacting being effected while said oil and said treating agent are in liquid state; and segregating an asphaltic oil of reduced metal contaminants.

2. The method of upgrading a petroleum oil residuum containing metal contaminants, said method comprising admixing said oil residuum with a treating agent comprising essentially condensed polynuclear aromatic compound having a C/ H ratio between about l/1 and about 2.5/1 and an average molecular weight within the range of from about 200 to about 600; maintaining the resulting admixture at a temperature within the range of from about 550 F. to about 900 F. for a period sufiicient to reduce the amount of the said metal contaminants in the said residuum; and segregating a treated residuum of reduced metal contaminants.

3. A method for producing a charge stock suitable for producing electrode grade coke which comprises treating an asphaltic residuum with a treating agent comprising condensed polynuclear aromatic compounds to remove metal contaminants from the asphaltic residuum and separating an asphaltic residuum of reduced metal content sufiicient to produce electrode coke therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 2,895,902 Peet July 21, 1959 

1. THE METHOD OF UPGRADING AN ASPHALTIC RESIDUAL OIL CONTAINING METAL CONTAMINANTS, SAID METHOD COMPRISING CONTACTING SAID ASPHALTIC RESIDUAL OIL WITH A TREATING AGENT COMPRISING ESSENTIALLY CONDENSED POLYNUCLEAR AROMATIC COMPOUND HAVING AN ATOMIC C/H RATION BETWEEN ABOUT 1/1 AND ABOUT 2.5/1 AND AN AVERAGE MOLECULAR WEIGHT WITHIN THE RANGE OF FROM ABOUT 200 TO ABOUT 600, SAID CONTACTING BEING EFFECTED WHILE SAID OIL AND SAID TREATING AGENT ARE IN LIQUID STATE; AND SEGREGATING AN ASPHALITIC OIL OF REDUCED MEAL CONTAMINANTS. 